This specification relates to interrogating an authentication device. Some products can authenticate product accessories to ensure that the accessories are approved by the manufacturer. For example, some smartphones can authenticate a battery upon installation of the battery, before charging, or at other times. In such cases, authentic batteries that are approved by the smartphone manufacturer include a secret function evaluator that can generate a correct response upon interrogation by the smartphone. For example, the smartphone can send a challenge to the battery, and an authentic battery can send the correct response to the smartphone.
Like reference numbers and designations in the various drawings indicate like elements.